1. Field of the Invention
The present invention relates to a reciprocatory piston type compressor adapted for a refrigeration system of e.g., an automobile air-conditioner. More particularly, it relates to a swash plate-operated refrigerant compressor capable of utilizing an injection of a refrigerant gas from a liquid-gas divider o a refrigeration system to enhance compressor discharge performance during the compression of refrigerant gas returning from an evaporator of the refrigeration system.
2. Related Art
A refrigeration system of an automobile air-conditioner includes a refrigerant compressor such as a fixed capacity swash plate-operated double-headed axial piston type compressor and a variable capacity swash plate-operated single-headed axial piston type compressor.
FIG. 6 illustrates a known refrigeration system including an evaporator 55, a refrigerant compressor 50 delivering therefrom a high pressure and high temperature refrigerant gas by compressing a refrigerant gas when it returns from the evaporator 55, a condenser 51 for condensing the refrigerant gas after compression when it is sent from the compressor, a first pressure reducer 52 for reducing a pressure level of the condensed refrigerant sent from the condenser 51, a liquid-gas divider 53 for dividing the condensed refrigerant into a refrigerant in the gas form and a refrigerant in the liquid form, and a second pressure reducer 54 for reducing a pressure level of the refrigerant in the liquid form by introducing therein from the liquid-gas divider 53. The pressure reduced liquid refrigerant sent from the second pressure reducer 54 is then evaporated in the evaporator 55 by absorbing heat from an exterior air to thereby cool the air. Namely, the refrigerant compressor 50, the condenser 51, the first pressure reducer 52, the liquid-gas divider 53, the second pressure reducer 54 and the evaporator 55 are sequentially connected by refrigerant conduits to form a closed refrigeration system. Further, the refrigerant compressor 50 is connected to the liquid-gas divider 53 by a refrigerant conduit 56 to introduce the divided refrigerant gas at a relatively high pressure from the liquid-gas divider 53 into the compressor 50. Namely, the high pressure refrigerant gas is injected from the divider 53 into the compressor 50 through the refrigerant conduit 56. The injection of the high pressure refrigerant gas can enhance the discharge performance of the compressor to thereby improve the refrigeration efficiency of the refrigeration system.
The Japanese Unexamined (Kokai) Patent Publication No. 62-175557 discloses a typical construction of the swash plate type refrigerant compressor capable of receiving an injection of the high pressure refrigerant gas from the liquid-gas divider. In accordance with the compressor construction of the above-mentioned Patent Publication No. '557, a cylinder block of the compressor is provided with a plurality of cylinder bores, and a suction chamber fluidly communicated with the cylinder bores via suction valves. The suction chamber has a subsidiary chamber capable of communicating with a particular one of the plurality of cylinder bores and a main suction chamber capable of communicating with the cylinder bores other than the particular cylinder bore. The subsidiary suction chamber is provided with an inlet port connected to an injection conduit so as to receive a high pressure refrigerant gas from the liquid-gas divider. Therefore, the high pressure refrigerant gas is injected from the subsidiary suction chamber into the particular cylinder bore.
Nevertheless, in the above-mentioned compressor of the Japanese Unexamined Patent Publication No. 62-175557, the injection of the high pressure refrigerant gas is given to only one of the plurality of cylinder bores, and accordingly enhancement of the overall discharge performance of the compressor must be limited, and therefore the injection of a high pressure refrigerant gas cannot satisfactorily contribute to an enhancement of the compressor discharge performance.
Further, if an amount of the injection of the high pressure refrigerant gas is increased to enhance the compressor discharge performance, the particular single cylinder bore to which the injection of the high pressure refrigerant gas is applied must be constantly subjected to a high pressure, and therefore such high pressure acts on a discharge valve of the particular cylinder bore to thereby reduce physical durability thereof.
Furthermore, in the case of the refrigerant compressors such as a vane type compressor, a rotary type compressor and a scroll type compressor, it is easy to meet structural requirements for receiving an injection of a high pressure refrigerant gas by employing a relatively simple change in the construction thereto.
Nevertheless, in the case of the reciprocatory piston type compressor, a very complicated construction must be provided for receiving an injection of a high pressure refrigerant gas into each of the plurality of cylinder bores.